Biocide impregnated fiber-reinforced sponge material

ABSTRACT

The present invention relates to a regenerated cellulose based sponge material with an inner viscose fiber reinforcement having a staple fiber length of 5-50 mm and impregnated with a biocide agent. Also disclosed is a regenerated cellulose based sponge material with an inner cotton fiber reinforcement having a staple fiber length of 5-50 mm and impregnated with a biocide agent. The coagulation and regeneration takes place in a bath that has a pH of 13 or higher and which includes Glauber&#39;s salt, NaOH and water.

This application is a 371 of PCT/EP97/04849 filed Sep. 6, 1997.

The present invention relates to a fiber-reinforced sponge cloth whichis produced by the viscose process and which makes a versatile cleaningand decontaminating cloth, especially for the private household.

Sponge cloth production by the viscose process is well known. First,pulp, especially wood pulp, is converted with sodium hydroxide andcarbon disulfide into an alkaline cellulose xanthate solution, so-calledviscose solution. At the same time, cotton noils are degreased withdilute, detergent-containing NaOH and mercerized. Viscose solution andcotton fibers are then mixed together to form a homogeneous mass,generally with the aid of a kneader. Glauber's salt (sodium sulfatedecahydrate) is then added and likewise mixed in uniformly. This spongecloth raw material is then applied to a foraminous endless belt towhichever depth is desired. The regeneration of the cellulose then takesplace in a heated, alkaline coagulation bath. It can also be carried outin an acidic medium, for example dilute sulfuric acid. In the process,the internal reinforcement becomes integrated into the sponge clothbody.

Glauber's salt has a very low melting point (about 32 to 33° C). Ittherefore melts in the coagulation bath and is dissolved out. Thedisappearing salt crystals leave pores and voids behind. Finally, thesponge cloth is washed out to rid it of salt residues and adheringreaction products. After drying, it is cut into narrow lengths, which inturn are rolled up. The roll material can then be end-itemed into clothsof the desired size. If desired, it can additionally be printedbeforehand.

However, fibre-reinforced sponge cloths are brittle in the dry state.They are therefore marketed in this form only in a few countries.Moistened sponge cloths, in contrast, are more flexible and have asignificantly better “hand”. To keep the sponge cloth moist, the spongecloth lengths are impregnated with the solution of a hygroscopic salt,especially magnesium chloride. Excess liquid is removed with the aid ofa pair of squeeze rolls. The moist cloths are then packaged, normally ina polymeric film However, inside the package, micro-organisms,especially bacteria and fungi, can multiply, which shows itself in theform of dark spots on the sponge cloths.

It is an object of the present invention to kill these microorganisms orat least inhibit their propagation.

We have found that this object is achieved by a sponge cloth which isbased on regenerated cellulose and has been provided with an internalreinforcement, wherefor the coagulation and regeneration takes place ina bath which has a pH of 13 of higher and which consists of Glauber'ssalt, NaOH and water and wherein the internal reinforcement consists ofviscose fibres having a staple fibre length of 5 to 50 mm and whichsponge cloth has been impregnated with a biocidally active agent.Viscose fibres are obtainable in a substantially more uniform qualitythan the hitherto customary cotton fibres. In addition, the ginning ofcotton fibres does not succeed in removing all the seeds and trash. Thisimpurity is particularly conspicuous in the case of undyed orlight-colored sponge cloths. The seeds are visible therein as smallblack spots. It is true that the seeds are removable, but this isrelatively costly. In addition, the color of natural cotton fibres issubject to fluctuations. Finally, cotton fibres have the disadvantagethat they have to be degreased beforehand. Residues of the degreasingsurfactants used tend to cause problems, especially due to foaming, inthe production of the sponge cloth. It was further known that biocidallyactive quaternary ammonium salts, specifically benzalkonium chlorides,lose their efficacy in the presence of cotton fibres (Martindale, TheExtra Pharmacopoeia, 28th ed., London [1982], page 549).

Preferred biocidally active agents for the purposes of the presentinvention are isothiazolone, benzisothiazolone and benzimidazolederivatives, especially those of the following formulae 1 to 12:

In the aforementioned formulae, R is an alkyl, alkenyl or alkadienylradical, which generally comprises 1 to 20 carbon atoms and ispreferably straight-chain. Of these, the straight-chain alkyl radicalshaving 6 to 18 carbon atoms are particularly preferred. The largestpracticable N-alkyl radical is stearyl. Compounds whose N-alkyl radicalcomprises 14 carbon atoms or fewer generally have higher bactericidaleffect. However, as the chain length decreases, the solubility in waterincreases. When more than one alkyl group is present, the total numberof carbon atoms present therein is preferably likewise not more than 20.In the compound of the formula 7, R may also be a chlorine atom. In thechlorine-substituted isothiazolones, i.e., compounds 6 to 8, the alkylgroup generally comprises only 1 to 12, preferably even only 1 to 8,carbon atoms. The second chlorine substituent enhances the bactericidaleffect of the compound and, what is more, reduces its solubility inwater. In the compounds of the formulae 9, 10 and 11, the alkyl radicalis generally shorter. It contains only 1 to 4 carbon atoms, and methyl,ethyl and propyl radicals are preferred in turn.

In addition, R can also be a cycloalkyl radical which generallycomprises 3 to 12 carbon atoms. In the chlorine-substitutedisothiazolone compounds of the formulae 6 to 8, the cycloalkyl radicalgenerally comprises only 3 to 8 carbon atoms, and the cyclohexyl radicalis particularly noteworthy. Particular preference is given to thecompounds of the formulae 1, 3, 6 and 9. The compound of the formula 12(2-methoxycarbonylaminobenzimidazole) is also known under the INN nameof carbendazim. Also suitable are, furthermore,1-butylcarbamoyl-2-methoxycarbonylaminobenzimidazole (benomyl),2-thiazol-4-ylbenzimidazole (thiobendazole) and2-furan-2-ylbenzimidazole (fuberidazole).

Fungicidal and/or bactericidal action is also exhibited by quaternaryammonium salts having long-chain, generally saturated, but alsounsaturated, alkyl groups having 6 to 24, preferably 10 to 18, carbonatoms. Of these cationic, surface-active ammonium salts, particularlysuitable ones are di(C₁₀-C₁₈)alkyl-dimethylammonium chlorides (such asdidecyldimethylammonium chloride), (C₈-C₁₈) alkyltrimethylammoniumchlorides (such as trimethyloctylammonium chloride,decyltrimethylammonium chloride and hexadecyltrimethylammoniumchloride), soyalkyltrimethylammonium chloride,dicocalkyldimethylammonium chloride, alkyl-benzyldimethylammoniumchlorides (such as benzyldimethylstearylammonium chloride,benzylcocalkyldimethylammonium chloride orcocalkyl(2,4-dichlorobenzyl)dimethylammonium chloride. Frequently,mixtures of quaternary ammonium salts of fatty acids of differentlengths are used (cocalkyl and soyalkyl each represent a mixture ofsaturated or unsaturated alkyl groups of varying length). The anion inthe ammonium salts need not necessarily be chloride. The anion mayequally well be bromide, acetate, propionate, sorbate, benzoate orsulfate. These compounds are described in EP-A 286 009, for example.

The present invention finally also provides a sponge cloth which isbased on regenerated cellulose and has been provided with an internalreinforcement, wherefore coagulation and regeneration takes place in abath which has a pH of 13 or higher and which consists of Glauber'ssalt, NaOH and water and wherein the internal reinforcement consists ofcotton fibres having a staple fibre length of 5 to 50 mm and whichsponge cloth has been impregnated with a bactericidally active agent.

The bactericidally active agent therein is preferably one of theisothiazolone, benzisothiazolone or benzimidazole derivatives alreadymentioned.

The bactericidal agents used in the sponge cloth of the invention mayalso be dipyridyl disulfide and its bis-N-oxide, specificallydipyridin-2-yl disulfide. It is further possible to use the 1-alkyl- and1-alkenyl-pyridinium salts (such as 1-laurylpyridinium chloride)likewise described in EP-A 286 009. It is also possible to use biguanidecompounds as described in U.S. Pat. No. 4 675 347. Also suitable arepenicillins, cephalosporins, tetracyclins and other antibacteriallyactive compounds, provided they are officially approved for thispurpose. Finally, it is also possible to combine a plurality of theaforementioned agents.

The biocidal impregnation may also be brought about by treating withglycerol or 1,2-propanediol (propylene glycol). To be effective, theyhave to be present in the sponge cloth in an amount which is sufficientto reduce the water activity (the so-called a_(w) value) to 0.9 or less.An a_(w) value of 0.85 or less will even inhibit the development of moldfungi (see E. Lück, Z Lebensm. Unters.-Forsch. 153 [1973] 42-52). Manyof the compounds mentioned are active not only against fungi andbacteria, but also against yeasts, algae and other microorganisms.

The weight proportion attributable to the biocidally active compound(s)depends on the species of microorganisms and the constitution of therespective compound. In the case of a(C₁₂-C₁₈)alkylbenzyldimethylammonium chloride, the fungicidallyeffective amount is about 1100 to 1600 ppm, based on the dry weight ofthe sponge cloth. In the case of didecyidimethylammonium chloride, 1 ppmis sufficient for an algicidal effect.

The biocidally active agent can be added to the moistening bathmentioned. The bath preferably contains a magnesium chloride solutionabout 2 to 8% by weight in strength, especially about 4% by weight instrength. This production process is particularly favorable with regardto equipment. However, it may also be added to a separate treatmentbath. The moistened sponge cloths contain about 0.01 to 0.4% by weight,preferably about 0.03 to 0.25% by weight, of MgCl₂, based on the dryweight of the sponge cloth. The impregnation with the hygroscopic saltand the impregnation with the biocidally active compound, however, arein principle independent of each other. Thus, even nonmoistened spongecloths can be antibacterial.

The cotton or viscose fibers serving as internal reinforcement in thesponge cloth of the present invention preferably have a staple fiberlength of 10 to 30 mm. The cotton fibers, as mentioned at the beginning,are degreased and optionally mercerized before use. The proportion ofthe dry weight of the sponge cloth attributable to the internalreinforcement is generally about 5 to 50% by weight, preferably 10 to40% by weight.

The rest of the production process then preferably takes the form,described at the beginning, of kneading the cotton or viscose fiberswith the viscose solution and subsequently also with Glauber's salt,spreading the mass obtained from the kneader onto a conveyor belt,coagulating by heating, washing and drying. The coagulation bathgenerally contains sodium hydroxide and is consequently stronglyalkaline (pH ≧13). Instead of an alkaline coagulation bath, it is alsopossible to use an acidic bath having a pH of about 1. It customarilycontains dilute sulfuric acid. In addition, the coagulation bath willusually also contain Glauber's salt.

We claim:
 1. A sponge cloth which is based on regenerated cellulose andhas been provided with an internal reinforcement consisting of viscosefibers having a staple fiber length of 5 to 50 mm, said sponge clothbeing obtained by a process comprising the steps of coagulating andregenerating the cellulose in a bath which has a pH of 13 or higher andwhich comprises Glauber's salt, NaOH and water, and impregnating thesponge cloth with a biocidally active agent.
 2. The sponge cloth ofclaim 1, wherein biocidally active agent is an isothiazolone,benzisothiazolone or benzimidazole compound.
 3. The sponge cloth ofclaim 1, wherein the biocidally active agent is a quaternary ammoniumsalt.
 4. The sponge cloth of claim 1, wherein the biocidally activeagent is glycerol or 1,2-propanediol.
 5. The sponge cloth of claim 1,wherein the staple fiber length of the viscose fibers is 10 to 30 mm. 6.The sponge cloth of claim 1, wherein the proportion of the dry weight ofthe sponge cloth attributable to the internal reinforcement is 5 to 50%by weight.
 7. The sponge cloth of claim 1, moistened with an aqueousmagnesium chloride solution.
 8. A sponge cloth which is based onregenerate cellulose and has been provide with an internal reinforcementconsisting of cotton fibers having a staple fiber length of 5 to 50 mm,said sponge cloth being obtained by a process comprising the steps ofcoagulating and regenerating the cellulose in a bath which has a pH of13 or higher and which comprises Glauber's salt, NaOH and water, andimpregnating the sponge cloth with a biocidally active agent.
 9. Thesponge cloth of claim 8, wherein the bactericidally active agent is anisothiazolone, benzisothiazolone or benzimidazole compound.
 10. Thesponge cloth of claim 8, wherein the staple fiber length of the cottonfibers is 10 to 30 mm.
 11. The sponge cloth of claim 8, wherein thebactericidally active agent is a penicillin, cephalosporin, tetracyclin,a pyridinium salt or a biguanide compound.
 12. The sponge cloth of claim8, wherein the proportion of the dry weight of the sponge clothattributable to the internal reinforcement is 5 to 50% by weight. 13.The sponge cloth of claim 8, moistened with an aqueous magnesiumchloride solution.
 14. The sponge cloth of claim 1, wherein thebactericidally active agent is applied subsequent to the regeneration ofthe cellulose.
 15. The sponge cloth of claim 8, wherein thebactericidally active agent is applied subsequent to the regeneration ofthe cellulose.